Rewrite Exponential Expressions Using Exponents

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Algebra 2 › Rewrite Exponential Expressions Using Exponents

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1

An account grows by 12% per year, so its value after $t$ years is multiplied by $(1.12)^t$. Rewrite $(1.12)^t$ in an equivalent form that reveals the monthly growth factor (assume 12 months per year).​​

$\left(1.12^{1/12}\right)^{12t}$

$\left(\dfrac{1.12}{12}\right)^{12t}$

$\left(1.12^{12}\right)^t$

$\left(1.12\right)^{t/12}$

Explanation

This question tests your ability to use exponent properties to transform exponential expressions into equivalent forms that reveal different information, like converting annual interest rates to monthly rates. The power-of-a-power property $(b^a$$)^c$ = b^(ac) lets us rewrite expressions like $(1.12)^t$ (12% annual growth) as ((1.12)^(1/12))^(12t) to reveal the monthly growth rate: we break each year into 12 months and find the factor that, when applied 12 times (raised to power 12), gives the yearly factor 1.12. The monthly factor is (1.12)^(1/12) ≈ 1.0095, meaning about 0.95% per month. Both forms equal the same value for any t, but one emphasizes annual compounding, the other monthly! To convert annual expression $(1.12)^t$ to monthly form: (1) Recognize that t years equals 12t months, (2) Want form (something)^(12t), (3) That something is (1.12)^(1/12) because ((1.12)^(1/12))^(12t) = (1.12)^((1/12)×12t) = $(1.12)^t$ by power-of-power property, (4) Calculate with calculator: (1.12)^(1/12) ≈ 1.0095, (5) So $(1.12)^t$ = ((1.12)^(1/12))^(12t), revealing monthly rate of about 0.95% (since 1.0095 = 1 + 0.0095). The exponent properties make the conversion systematic! Choice B correctly applies the power-of-a-power property to transform the expression and identifies the equivalent monthly rate. Choice C divides the annual factor by 12 to get monthly (1.12/12 ≈ 0.093), but this gives SIMPLE interest division, not compound! For compound interest, the monthly factor isn't found by division—we need (1.12)^(1/12), which is the 12th root of 1.12 ≈ 1.0095. Division would work for simple interest, but compound interest requires the fractional exponent! The power-of-a-power property $(b^a$$)^c$ = b^(ac) is your main tool for time-base conversion: to convert annual rate factor $b^t$ to monthly, write as ((b)^(1/12))^(12t)—take 12th root of b for monthly factor, raise to 12t (12 months times t years). This property is foundation of all time-base transformations!

2

Rewrite $\dfrac{(1.10)^{5t}}{(1.10)^{2t}}$ as a single exponential expression using the quotient of powers property.​​

$(1.10)^{7t}$

$(1.10)^{3t}$

$(1.10)^{(5/2)t}$

$(1.10)^{10t}$

Explanation

This question tests your ability to apply the quotient of powers property to simplify exponential expressions. The quotient of powers property states that $b^m$ / $b^n$ = b^(m-n) when dividing powers with the same base—you subtract the exponent in the denominator from the exponent in the numerator. For (1.10)^(5t) / (1.10)^(2t), both terms have base 1.10, so we can apply the property: (1.10)^(5t) / (1.10)^(2t) = (1.10)^(5t-2t) = (1.10)^(3t). The key is recognizing that 5t - 2t = 3t! To verify this makes sense: (1) Division undoes multiplication, so we're asking "how many times do we multiply by 1.10^(2t) to get 1.10^(5t)?", (2) We need to multiply by 1.10 an additional 3t times (since 2t + 3t = 5t), (3) So the quotient is (1.10)^(3t), (4) Check: (1.10)^(2t) × (1.10)^(3t) = (1.10)^(2t+3t) = (1.10)^(5t) ✓. The property provides a direct route without expanding! Choice B correctly applies the quotient of powers property, subtracting the exponents to get (1.10)^(3t). Choice A incorrectly adds the exponents (5t + 2t = 7t) instead of subtracting them—this would be the rule for multiplying powers with the same base, not dividing! Remember: multiply powers → add exponents, divide powers → subtract exponents. This is a fundamental pattern in exponent algebra! The quotient of powers property $b^m$ / $b^n$ = b^(m-n) simplifies division of exponential expressions: always subtract the bottom exponent from the top exponent when bases match. This property, combined with the product property $(b^m$ × $b^n$ = b^(m+n)), forms the foundation for all exponential algebra—master these two and you can handle any exponential simplification!

3

A culture of bacteria triples every day. If $t$ is measured in weeks, its growth factor can be written as $3^{7t}$ (since 7 days per week). Rewrite $3^{7t}$ using exponent properties as a power of a power so it looks like a weekly growth factor raised to $t$.

Which rewrite is correct?

$\left(3^{7}\right)^{t}$

$\left(3^{1/7}\right)^{t}$

$\left(3^{7t}\right)^{7}$

$\left(3^{t}\right)^{7}$

Explanation

This question tests your skill in rewriting exponential expressions using power-of-a-power to shift from daily to weekly growth factors while keeping the overall model equivalent. The property $(b^a$$)^c$ = b^(a c) lets us transform $3^{7t}$ (tripling every day over 7t days) into $(3^7$$)^t$, where $3^7$ is the weekly growth factor since seven daily triplings multiply to $3^7$, or 2187 times per week. This form emphasizes growth per week raised to t weeks, making it easier to think in weekly terms. To rewrite: (1) Identify the weekly factor as $(daily)^7$ = $3^7$, (2) Raise to t: $(3^7$$)^t$ = $3^{7t}$, confirming equivalence via the property. Choice B correctly applies this to show the weekly factor $3^7$ raised to t, matching the requested form. Choice C gives $(3^t$$)^7$ = $3^{7t}$ too, but it's raised to 7 instead of t, so it doesn't present as $weekly^t$—note the order matters for the interpretation! Use this strategy for any period change: group the base by the new time unit using exponents, and verify by expanding—you're mastering these conversions beautifully!

4

A tech company’s revenue is modeled by $R(t)=R_0,8^t$, where $t$ is in years. Rewrite $8^t$ in terms of base $2$.

(Use the power-of-power property.)

$8^t = 2^{t/3}$

$8^t = 2^{3+t}$

$8^t = 2^{3t}$

$8^t = 6^t$

Explanation

This question tests your ability to rewrite exponential expressions by changing the base using exponent properties, specifically for powers where the bases are related like 8 = $2^3$. The power-of-a-power property $(b^a$$)^c$ = b^(ac) lets us express $8^t$ as $(2^3$$)^t$ = $2^{3t}$, transforming the base while adjusting the exponent to keep equivalence— this reveals the growth in terms of doubling (base 2) tripled in exponent due to 8 being 2 cubed. To rewrite: factor the base $(8=2^3$), apply the property to multiply exponents: 3t = 3t, so $2^{3t}$ matches $8^t$ for any t— you can check with t=1: $8^1$=8, $2^{3}$=8. Choice C correctly uses the power-of-a-power property to convert to base 2 with the multiplied exponent 3t. Choice A divides the exponent by 3 instead of multiplying, a common slip when mixing up roots versus powers—remember, since 8 is 2 raised to 3, we multiply the exponent by 3, not divide! The strategy extends: for any b = $a^k$, then $b^t$ = $a^{k t}$ via power-of-a-power—practice with $9^t$ = $3^{?}$ (answer: 2t since $9=3^2$). Great job; this base-changing technique will help in many modeling problems, keep practicing!

5

An investment grows according to $A(t)=P,(1.15)^t$ (with $t$ in years). Which statement correctly interprets the transformation $$ (1.15)^t = \left(1.15^{1/12}\right)^{12t}? $$

It shows the account earns 15% each month for $12t$ months.

It changes the annual rate to a simple monthly rate of $0.15/12$.

It shows the same growth written using a monthly growth factor applied over $12t$ months.

It shows the account earns $1.15^{12}$ per year instead of $1.15$ per year.

Explanation

This question tests your ability to interpret the meaning of exponential transformations when converting between different time periods in growth models. The transformation $(1.15)^t = \left( (1.15)^{1/12} \right)^{12t}$ uses the power-of-a-power property to rewrite annual growth in terms of monthly growth: the annual factor 1.15 (representing 15% annual growth) is converted to its monthly equivalent by taking the 12th root, giving $(1.15)^{1/12} \approx 1.0117$ (about 1.17% monthly growth). This monthly factor is then applied 12t times (for 12t months in t years), maintaining the same overall growth but revealing the monthly compounding structure. The key insight is that both expressions produce identical values for any t, but the right side makes the monthly growth rate explicit! To understand why this works: (1) The original $(1.15)^t$ means "multiply by 1.15 for each of t years", (2) The transformed $\left( (1.15)^{1/12} \right)^{12t}$ means "multiply by $(1.15)^{1/12}$ for each of 12t months", (3) By the power-of-a-power property, $\left( (1.15)^{1/12} \right)^{12t} = (1.15)^{ (1/12) \times 12t } = (1.15)^t$, (4) So we get the same result but expressed differently. The transformation doesn't change the growth—it reveals it at a different time scale! Choice B correctly states that the transformation shows the same growth written using a monthly growth factor applied over 12t months. Choice A incorrectly claims the account earns 15% each month, but $(1.15)^{1/12} \approx 1.0117$ represents about 1.17% monthly growth, not 15%! The 15% is the annual rate, and when compounded monthly, you need the 12th root to find the equivalent monthly rate. This is a critical distinction in compound interest calculations! When interpreting exponential transformations: (1) The base raised to a fractional power gives the rate for that fraction of the time period, (2) (Annual factor)$^{1/n}$ gives the factor for 1/n of a year, (3) The exponent in the outer parentheses (like 12t) counts how many of these smaller periods occur. Always verify that the transformation maintains equality—the power-of-a-power property ensures it does!

6

A population is modeled by $P(t)=P_0(1.08)^t$, where $t$ is in years. Rewrite the growth part $(1.08)^t$ to show an equivalent form with a quarterly growth factor raised to the number of quarters.

(Use the power-of-power property.)

$(1.08)^t = \left((1.08)^{1/4}\right)^{4t}$

$(1.08)^t = \left((1.08)^{1/4}\right)^{t/4}$

$(1.08)^t = \left((1.08)^{1/t}\right)^{4}$

$(1.08)^t = \left((1.08)^{4}\right)^{t}$

Explanation

This question tests your ability to apply exponent properties to rewrite growth expressions in terms of different time intervals, such as quarterly from annual. The power-of-a-power property $(b^a$$)^c$ = b^(a*c) enables us to transform $(1.08)^t$ into $((1.08)^{1/4}$$)^{4t}$, where $(1.08)^{1/4}$ is the quarterly factor—applied 4 times per year over t years, equaling 4t quarters, and both expressions match since (1/4)*4t = t. For the conversion: note t years = 4t quarters, seek (quarterly $factor)^{4t}$, set quarterly factor to $(1.08)^{1/4}$ so the property multiplies exponents back to t— you can verify with a calculator if needed, but the focus is on the algebraic equivalence. Choice A correctly implements the power-of-a-power property to produce the quarterly form with the exponent 4t for total quarters. Choice B reverses the process by raising to the 4th power inside, leading to $(1.08)^{4t}$, which overstates growth—a frequent error is confusing roots with powers, but remember to take the root (divide exponent) when breaking into more periods! To master this, use the formula: for m periods per year, rewrite $b^t$ as $(b^{1/m}$$)^{m t}$—the exponents multiply to t, preserving value. Keep up the excellent work; experiment with m=2 for semi-annual to see how this strategy transfers seamlessly!

7

Rewrite $\dfrac{(1.10)^{5t}}{(1.10)^{2t}}$ as a single exponential expression using the quotient of powers property.

$(1.10)^{3t}$

$(1.10)^{7t}$

$(1.10)^{(5/2)t}$

$(1.10)^{10t}$

Explanation

This question tests your ability to apply the quotient of powers property to simplify exponential expressions. The quotient of powers property states that $b^m$ / $b^n$ = b^(m-n) when dividing powers with the same base—you subtract the exponent in the denominator from the exponent in the numerator. For (1.10)^(5t) / (1.10)^(2t), both terms have base 1.10, so we can apply the property: (1.10)^(5t) / (1.10)^(2t) = (1.10)^(5t-2t) = (1.10)^(3t). The key is recognizing that 5t - 2t = 3t! To verify this makes sense: (1) Division undoes multiplication, so we're asking "how many times do we multiply by 1.10^(2t) to get 1.10^(5t)?", (2) We need to multiply by 1.10 an additional 3t times (since 2t + 3t = 5t), (3) So the quotient is (1.10)^(3t), (4) Check: (1.10)^(2t) × (1.10)^(3t) = (1.10)^(2t+3t) = (1.10)^(5t) ✓. The property provides a direct route without expanding! Choice B correctly applies the quotient of powers property, subtracting the exponents to get (1.10)^(3t). Choice A incorrectly adds the exponents (5t + 2t = 7t) instead of subtracting them—this would be the rule for multiplying powers with the same base, not dividing! Remember: multiply powers → add exponents, divide powers → subtract exponents. This is a fundamental pattern in exponent algebra! The quotient of powers property $b^m$ / $b^n$ = b^(m-n) simplifies division of exponential expressions: always subtract the bottom exponent from the top exponent when bases match. This property, combined with the product property $(b^m$ × $b^n$ = b^(m+n)), forms the foundation for all exponential algebra—master these two and you can handle any exponential simplification!

8

A quantity follows the model $Q(t)=Q_0,(1.02)^{12t}$, where $t$ is in years. Which equivalent form reveals the annual growth factor?

$Q(t)=Q_0,\left(1.02^{12}\right)^{t}$

$Q(t)=Q_0,\left(1.02^{1/12}\right)^{t}$

$Q(t)=Q_0,(1.02)^{t}$

$Q(t)=Q_0,\left(\dfrac{1.02}{12}\right)^{t}$

Explanation

This question tests your ability to recognize and transform between different time scales in exponential models by identifying which form reveals the annual growth factor. The given model Q(t) = Q₀(1.02)^(12t) has t in years but shows monthly compounding: the exponent 12t counts months (12 months per year × t years), and 1.02 is the monthly factor (2% monthly growth). To find the annual factor, we need to determine what factor, when applied once per year, gives the same growth as applying 1.02 twelve times per month. This is $(1.02)^12$! Using the power-of-a-power property in reverse: (1.02)^(12t) = $((1.02)^12$$)^t$, where $(1.02)^12$ ≈ 1.268 is the annual factor (about 26.8% annual growth). To verify the transformation: (1) Original: Q₀(1.02)^(12t) means "multiply by 1.02 for each of 12t months", (2) Need form Q₀(annual $factor)^t$ for t years, (3) In one year (t=1), the original gives $Q₀(1.02)^12$, (4) So annual factor = $(1.02)^12$, (5) Rewrite: Q₀(1.02)^(12t) = $Q₀((1.02)^12$$)^t$ by power-of-a-power property. Both forms are equivalent but emphasize different time scales! Choice B correctly identifies Q(t) = $Q₀((1.02)^12$$)^t$ as revealing the annual growth factor $(1.02)^12$. Choice C incorrectly uses (1.02)^(1/12), which would be going the wrong direction—this would give a growth factor for 1/12 of a month, not for a full year! When the original has more frequent compounding (monthly), we need to raise to a power $(^12$) to get less frequent (annual), not take a root (^(1/12)). The direction matters! When converting between time scales in exponential models: (1) More frequent to less frequent: raise to a power (monthly to annual: ^12), (2) Less frequent to more frequent: take a root (annual to monthly: ^(1/12)). The exponent in the model tells you the time unit: if you see b^(nt) where n is a number and t is time, then n tells you how many sub-periods per t!

9

A savings account has an annual growth factor of $1.06$. Which is the approximate monthly growth factor? (Use $1.06^{1/12} \approx 1.0049$.)​​

$1.06^{12} \approx 2.01$

$1.06^{1/12} \approx 1.0049$

$1.06/12 \approx 0.0883$

$1.06^{1/6} \approx 1.0097$

Explanation

This question tests your ability to identify the correct monthly growth factor when given an annual growth factor, using the concept of compound interest and fractional exponents. The key insight is that to find a monthly factor that compounds to give the annual factor, we need the 12th root of the annual factor: if the monthly factor is m, then $m^12$ = 1.06, so m = (1.06)^(1/12). Using a calculator, (1.06)^(1/12) ≈ 1.0049, meaning about 0.49% monthly growth. This makes sense: 0.49% monthly compounded 12 times gives approximately 6% annually! To verify: (1) Monthly factor m must satisfy $m^12$ = 1.06 (compound monthly to get annual), (2) Taking 12th root of both sides: m = (1.06)^(1/12), (3) Calculate: (1.06)^(1/12) ≈ 1.0049, (4) Check: $1.0049^12$ ≈ 1.0600 ✓, (5) So monthly growth is about 0.49% (since 1.0049 = 1 + 0.0049). The fractional exponent gives the exact compound rate! Choice C correctly identifies (1.06)^(1/12) ≈ 1.0049 as the monthly growth factor. Choice A incorrectly divides 1.06 by 12 to get 0.0883, but this would mean the account SHRINKS each month (factor less than 1)! This error comes from confusing growth factors with growth rates: the annual RATE is 6% = 0.06, but the annual FACTOR is 1.06 = 1 + 0.06. Even if we divided the rate 0.06/12 = 0.005, the monthly factor would be 1.005, not 0.0883! For compound interest conversions: (1) Annual factor to monthly: take 12th root, (2) Annual factor to daily: take 365th root, (3) General rule: (annual factor)^(1/n) gives the factor for 1/n of a year. Never divide the factor itself—always use fractional exponents for compound interest! The difference between simple and compound interest is crucial: simple interest would divide the rate, but compound interest requires the root!

10

A quantity is multiplied by $(1.05)^t$ after $t$ years. Which expression is equivalent and reveals the daily growth factor (assume 365 days per year)?

$\left(1.05^{1/365}\right)^{365t}$

$\left(\dfrac{1.05}{365}\right)^{365t}$

$\left(1.05\right)^{t/365}$

$\left(1.05^{365}\right)^{t}$

Explanation

This question tests your ability to use exponent properties to transform exponential expressions into equivalent forms that reveal different information, like converting annual growth rates to daily rates. The power-of-a-power property $(b^a$$)^c$ = b^(ac) lets us rewrite expressions like $(1.05)^t$ (5% annual growth) as ((1.05)^(1/365))^(365t) to reveal the daily growth rate: we break each year into 365 days and find the factor that, when applied 365 times (raised to power 365), gives the yearly factor 1.05. The daily factor is (1.05)^(1/365) ≈ 1.000134, meaning about 0.0134% per day. Both forms equal the same value for any t, but one emphasizes annual compounding, the other daily! To convert annual expression $(1.05)^t$ to daily form: (1) Recognize that t years equals 365t days, (2) Want form (something)^(365t), (3) That something is (1.05)^(1/365) because ((1.05)^(1/365))^(365t) = (1.05)^((1/365)×365t) = $(1.05)^t$ by power-of-power property, (4) Calculate with calculator: (1.05)^(1/365) ≈ 1.000134, (5) So $(1.05)^t$ = ((1.05)^(1/365))^(365t), revealing daily rate of about 0.0134%. The exponent properties make the conversion systematic! Choice A correctly applies the power-of-a-power property to transform the expression and identifies the equivalent daily rate. Choice D divides the annual factor by 365 to get daily (1.05/365 ≈ 0.00288), but this gives SIMPLE interest division, not compound! For compound interest, the daily factor isn't found by division—we need (1.05)^(1/365), which is the 365th root of 1.05 ≈ 1.000134. Division would give a daily simple interest rate, but compound interest requires the fractional exponent! The power-of-a-power property $(b^a$$)^c$ = b^(ac) is your main tool for time-base conversion: to convert annual rate factor $b^t$ to daily, write as ((b)^(1/365))^(365t)—take 365th root of b for daily factor, raise to 365t (365 days times t years). For very small time periods like days, the fractional power gives a factor very close to 1, but when compounded many times (365 days), it produces the full annual growth!

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